Wednesday, 16 November 2016

Has anyone ever seen a black hole?

The answer is yes. Actually, there are black holes out there that anyone can see and you don't even need a gigantic telescope for it. Surprising, isn't it? Aren't black holes supposed to swallow all matter that comes too close and aren't they supposed to be so massive that even light can't escape from them? Yes, of course, but the interesting bit happens just before the matter disappears in the apparently bottomless, black void.

Imagine this incredible black hole, a sort of cosmic whirlpool that attracts anything unfortunate enough to come too close. Entire stars are being ripped apart by its unequalled gravitational pull and form dense clouds of matter around the hole before being absorbed. Pressure increases up to a point that the highly compressed gas begins to emit vast quantities of radiation in all frequencies of the electromagnetic spectrum, also in visible light; radiation that only just manages to escape from the boundaries of the black hole. So if we want to find a black hole, you don't have to look for a black spot in space but for an unusually bright spot! A spot so bright that, even though perhaps only a thousand lightyears across, it emits so much light and other radiation as an entire galaxy!

Now have a look at my sketch. The object in question is M77, a very large barred-spiral galaxy, nearly twice the diameter of our Milky Way. You can clearly see its spiral structure and the bar-like structure at its centre's more than obvious. I was also thrilled to be able to make out the extremely faint halo that surrounds it and which also consists of many billions of stars. But the most interesting part is its core. Look how small and bright it is! It alsmost looked stellar through my telescope! This is what scientists call an Active Galactic Nucleus; an extremely compact core because of the accretion of vast quantities of matter by the supermassive black hole at its centre, which possibly contains a mass of 15 million suns. These "AGNs" are the most luminous objects in the entire universe and this particular one's probably the closest to Earth, being at a distance of merely 47 million lightyears. These days scientists believe that every galaxy has a black hole in its core which acts like the gravitational engine that makes it swirl, grow, create stars and hence create life. But this one must definitely be one of the biggest in our backyard. Get your telescope out and have a look at it too!